This is a classic case for use of a flag variable. 

# init variable to show we're not in the blcok
my $in_block = 0;

while ( <> ) # process line by line
{
    $in_block = 1 if /^head/; # test for start of block and
                              # set flag true if needed
    print if $in_block; # print if we're in the block
    $in_block = 0 if /tail$/; # test for end of block and
                              # set flag false if needed
}

[download]

Sorry if I misunderstood your question, but according to the way I read it I think this is close. Given this file: 

fvewvwef vfewejmnvwev evfjerwvnrevjwe
wervkjvwe wevrjvrenwvr head
vfjlevnerojvnerve
head refejrverjvnerjovnerojvn ercjncer
rljnelrkvnervervekjnve tail fknvbekjev
nweclkneclknerclkernclenelrknclencekn
cwlknelcnlcwnejnrjnrjcnjcncjncnccjn tail
vjenvlejnvlejnrvlejnvejnvejnvejnvejvnejv
head efcjonecjnercjnerjcnerjnc
crjencerjncejlrcn
tail

[download]

I get this output: 

head refejrverjvnerjovnerojvn ercjncer
rljnelrkvnervervekjnve tail fknvbekjev
nweclkneclknerclkernclenelrknclencekn
cwlknelcnlcwnejnrjnrjcnjcncjncnccjn tail
head efcjonecjnercjnerjcnerjnc
crjencerjncejlrcn
tail

[download]

Sometimes a simple procedural style works really well, even if you have bells and whistles available. This could be written the same in almost any language. Perl just makes it easier.



Christopher E. Stith

In reply to Re: Extracting blocks of text by mr_mischief
in thread Extracting blocks of text by walker

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